jee-main 2014 Q75

jee-main · India · 06apr Sine and Cosine Rules Heights and distances / angle of elevation problem

A bird is sitting on the top of a vertical pole 20 m high and its elevation from a point $O$ on the ground is $45 ^ { \circ }$. It flies off horizontally straight away from the point $O$. After one second, the elevation of the bird from $O$ is reduced to $30 ^ { \circ }$. Then the speed (in m/s) of the bird is
(1) $20 \sqrt { 2 }$
(2) $20 ( \sqrt { 3 } - 1 )$
(3) $40 ( \sqrt { 2 } - 1 )$
(4) $40 ( \sqrt { 3 } - \sqrt { 2 } )$

A bird is sitting on the top of a vertical pole 20 m high and its elevation from a point $O$ on the ground is $45 ^ { \circ }$. It flies off horizontally straight away from the point $O$. After one second, the elevation of the bird from $O$ is reduced to $30 ^ { \circ }$. Then the speed (in m/s) of the bird is\\
(1) $20 \sqrt { 2 }$\\
(2) $20 ( \sqrt { 3 } - 1 )$\\
(3) $40 ( \sqrt { 2 } - 1 )$\\
(4) $40 ( \sqrt { 3 } - \sqrt { 2 } )$

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